Blending agents for mineral oils



United States Patent ()fiice Patented Aug. 14, 1956 BLENDING AGENTS FOR MINERAL OILS Louis A. Mikeska, Westfield, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware N0 Drawing. Application May 20, 1952, Serial No. 288,955

4 Claims. Cl. 252-321 This invention relates to oil compositions and particularly to lubricating oils in which an additive has been incorporated to improve the properties of the same.

Modern developments in the design of internal combustion engines, with increasing engine speeds and compression ratios, have imposed a severe strain on the lubricants employed. In particular the crankcase oil is raised to a high temperature, and in the course of its circulation through the engine is rapidly exposed to air under conditions highly conducive to destructive oxidation. Oxidative breakdown of the oil results in the formation of acidic products which corrode bearing surfaces and do considerable harm to the engine generally. Furthermore, the metallic corrosion products have the effect of catalyzing further oxidative breakdown of the oil.

It is also known that in modern internal combustion engines, such as aviation gasoline engines operating at relatively high temperatures due .to their high power output or in high speed Diesel engines due to incomplete combustion, piston rings have a tendency to become stuck in grooves. Lacquer and carbon formation appear to be the principal reasons for this occurrence. Moreover, scuffing of top lands due to the formation of hard carbon, particularly when using high viscosity index oils, may cause serious damage to the engine.

It has been found, in accordance with the present invention, that destructive oxidation of lubricating oils and deposition of carbon and lacquer may both be substantially reduced by the addition to the oil of a small amount of a new additive. This additive may be described as an ester of a hydrocarbon substituted hydroxy phosphonic acid. The esters of the present invention impart potent antioxidant properties to mineral oil compositions in which they are dissolved. In a preferred embodiment of the present invention, however, a heavy I "wherein R1 is selected from the group consisting of hydrogen and hydrocarbon radicals having in the range of l to 12 carbon atoms, and R2 is selected from the group consisting of hydrogen, hydrocarbon radicals, sulfurized hydrocarbon radicals, and alkyl phenol sulfide radicals having in the range of 1 to 30 carbon atoms, at least one R2 being an organic group. It is preferred that the molecule contain at least a total of 16 carbon atoms if it is used as an additive for lubricating oils in order to form compounds soluble therein.

R1 is preferably a straight or branched chain alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, tert.-butyl, n-hexyl, isooctyl, Z-ethylhexyl, decyl, dodecyl and the like. It may also represent other hydrocarbon radicals such as cycloalkyl, aralkyl, aryl, or alkaryl groups. Specific examples of these include methylcyclohexyl, ethylcyclohexyl, phenylethyl, phenylpropyl, phenyl, cresyl, tart-butyl phenyl, and the like groups. R1 preferably has in the range of 0 to 8 carbon atoms since such compounds are readily prepared and raw stocks are easily obtainable.

R2 may be one of the hydrocarbon groups mentioned in connection with R1 although it preferably has at least 12 carbon atoms, more preferably 12 to 24 carbon atoms. Thus it may be a tetradecyl, heaxdecyl, octadecyl, tetracosyl, and other higher straight and branched alkyl groups including those derived from Waxes and the like. R2 may also be an alkenyl radical such as decenyl, octadecenyl, Ctr-C24 polypropylenes, dechlorinated waxes, cracked gasolines, and the like. R2 may consist of other hydrocarbon, sulfur-containing hydrocarbon, and the like groups derived from various alcohols, sulfurized alcohols, phenols, alkyl phenol sulfides and the like as hereinafter described.

The esters of the present invention are readily prepared. In a first step, an aldehyde or ketone is condensed with phosphorus trichloride, and the resulting trichloro condensation product hydrolyzed to produce a hydroxy phosphoric acid having the general formula OOH OH OH wherein R1 has the above-defined meaning. Conveniently, the aldehyde may be formaldehyde, but alkyl aldehydes are preferred in order to form hydroxy alkyl phosphonic acids. For example, an Oxo aldehyde, derived from the catalytic oxonation of an olefin with carbon monoxide and hydrogen is a suitable, highly branched feed stock.

The hydroxy phosphonic acid is then esterified by reaction with an alcohol or phenol or various derivatives of these compounds. The esterification reaction is generally carried out with one to two mols of alcohol or phenol per mol of phosphonic acid, the ester radical being tied to the phosphorus atom. The complete esterification of the phosphorus hydroxy groups is sometimes difiicult, and therefore only a partial ester will be formed in those cases. Specific aliphatic alcohols include the lower alkyl alcohols, cetyl alcohol, lauryl alcohol, isodecyl 0x0 alcohol, isotridecyl Oxo alcohol, rhodinol, tetradecanols and tetradecenols, oleyl alcohol, and other saturated and unsaturated aliphatic alcohols. Sulfur derivatives of these alcohols are also suitable as sulfur imparting agents. These are conveniently prepared by sulfurizin-g unsaturated alcohols, such as oleylalcohol, with elemental sulfur by procedures well known to the art. Such sulfurized alcohols include Z-dodecylthioethanol, 3 tert. octylthiopropanol, 2 benzylthioethanol, and the like.

Phenols and alkyl phenols may be used as esterifying agents. Such compounds include phenol, cresol, naph thol, butyl phenol, tert.-octyl phenol, various dialkyl phenols, wax phenols, and the like.

Alkyl phenol sulfides are also excellent esterifying' agents. These compounds are prepared by known meth ods such as by treating an alkyl phenol with a sulfur chloride to form a sulfur bridge of about 1 to 5 sulfur atoms connecting two alkyl phenol radicals. Generally,

only one hydroxyl group in the alkyl phenol sulfide will esterify leaving the other hydroxyl group free. Typical alkyl phenol sulfides may be prepared from the abovementioned alkyl phe nols, generally the alkyl groups having in the range of 4 to 12 carbon atoms. Specific compounds include n-butyl, tert.-amyl, n-hexyl, tert.-octyl, ditert-octyl and n-decyl phenol sulfides.

The thioalcohol and thiophenol homologues of the above-named compounds as well as other sulfur-containing compounds may also be employed in the esterification reaction. Such compounds include mercaptans, xanthates, thioxanthates, thiophenols, thiocarbamates, etc. To obtain the latter products, the intermediate phosphonic acid chloride,v

is, condensed with a xanthate, carbamate, or a mercaptide, rather than direct esterification of the .phosphonic acid.

The esters described above may be used as mineral oil additives, particularly as anti-oxidant additives and corrosion inhibitors. However, in a preferred embodiment of the'present invention, the metal salts of the esters are prepared. The incorporation of metal into the compound results in. products that have potent detergency and sludge dispersing properties and is very desirable when the material is used in internal combustion engine lubricants and the like.

The metal salts are conveniently prepared by treating the partial esters (containing at least one phosphorus hydroxy group) with a basic metal neutralizing agent such as a finely divided oxide or hydroxide of the desired metal, at least suflicient neutralizing agent being used to neutralize completely the partial esters. Preferably, the metal of the neutralizing agent is an alkaline earth metal such as calcium, barium, magnesium and strontium. Metal salts of other polyvalent heavy metals are also quite useful. These include nickel, cobalt, tin, lead, zinc, copper, aluminum, iron, mangansese, and the like. Salts of monovalent metals such as sodium, potassium, lithium, and the like are generally less preferred because the resulting compounds are likely to be water soluble and are not sufficiently potent as detergent additives. The metal may be in the form of metal carbides, metal alkoxides and the like when it is employed in making the metal salt.

'It is generally desired to use an amount of neutralizing agent that is slightly in excess of that required forneutralizing the ester heretofore described. In the case of some compounds, it may be desired to use amounts considerably in excess of neutralization requirements. The metal will generally attach to the free hydroxyl radical connected to the phosphorus atom. However, if the phosphonic acid has been esterified with an alkyl phenol sulfide or other material that contains a free phenohydroxyl group, the metal may also replace the hydrogen on that hydroxyl group or form a bridge between the hydroxyl group on the phenol radical and that'on the phosphorus atom.

The basic metal neutralizing agent is preferably added slowly-to the mixture with stirring, a sufficient length of time being employed during the reaction to insure its completion. The reaction is generally carried out at a temperature in the range of about 10 to 100 C., though higher temperatures may be employed when necessary. In-some cases, neutralization may be carried out in aque ous solutions. When anhydrous conditions are employed, any water formed in the neutralization step may be removed by conventional drying or distillation procedures. The reaction mixture may then be filtered to remove insoluble reactants or reaction products.

'The neutralization reaction is-conveniently carried out inan inert solvent such as ether, although it may be conducted in a lubricant base oil, particularly where the metal salt is used as a lubricant additive. Thus, a concentrate containing in the range of about 20 to 50% of the partial ester in a lubricant base oil is treated with a neutralizing agent as heretofore described.

In another embodiment of the present invention, the esters of the hydroxy phosphonic acids are treated with a reactive sulfur and phosphorus-containing material. It is preferable to employ a sulfide of phosphorus such as P253, P255, P483, or P437, or mixtures thereof. Mixtures of elemental sulfur and elemental phosphorus may likewise be employed, in which case powdered sulfide and white phosphorus are conveniently used. Likewise, a mixture of one or more sulfides of phosphorus and elemental sulfur and/ or elemental phosphorus may be used. Oxides of phosphorus such as P205, or P203, may also be employed to formphosphoric and phosphorous esters.

The amounts of sulfur and phosphorus which are advantageously employed will depend to a large extent on the amount of phosphorus and sulfur that it is desired to introduce into the product. Generally the sulfide of phosphorus will react with a free hydroxyl radical, particularly that attached. to the hydrocarbon radical of the molecule. Double bonds in the compound may also react with the sulfide of phosphorus. Generally, about 0.2 to 1.5 mols of a sulfide of phosphorus may be used for each mol of ester. The temperature at which the reaction is carried out may be in the range of about 200500 F., preferably about 250-400 F. The time required to complete the reaction will range from about 1 to 10 hours.

The phosphosulfurization reaction is conveniently carried out in an organic solvent. The solvent should be relatively inert to phosphorus and sulfur. Such solvents include, for example, benzene, o-dichlorobenzene, dioxane and the like. Conveniently, the reaction is carried out at the refluxing temperature of the solvent. This reaction may also be carried out in the presence of a lubricant base oil stock in order to prepare a concentrate for use in blending with finished lubricants.

The phosphosulfurized esters may also be used as additives, although it is preferred that the metal salt of this material be formed. The metal salt is conveniently produced by the procedure heretofore described in connection with the preparation of the metal salts of the esters. Although the alkaline earth metal salts are generally preferred, other poly-valent heavy metal salts of the types described above may also be prepared.

The additives of the present invention are preferably added to mineral oils in proportions ranging from 0.01% to 15% the proportion being preferably about 0.1 to 5.0% when employed as corrosion inhibitors and detergents in mineral lubricating oils. The proportions giving the best results will vary somewhat according to the nature of the additive and the specific quality characteristics -of the oil to .be improved by the use of the additive. For commercial purposes, when the additives are to be employed in mineral lubricating oils, it :is convenient 'to prepare concentrated oil solutions as described above in which the amount of additive in the compositions ranges from about 20 to 50% by weight, and to transport and store'them in such form. In preparing lubricating oil compositions for use as crankcase lubricants, the additive concentrate is merely blended with the base oil in the required amount.

The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in the heavy duty type of lubricating oils which have been compounded with such detergent type additives as metal soaps, metal petroleum -sulfonates, metal :phenates, imetal .alcoholates, metal alkyl phenol sulfides, metal :organo phosphates, .phosphites, .thiophosphates and thiophosphites, :guanidine :salts, metal uranthates and .thioxanthates, metal thiocarbamates, and the like. Other types of additives, V such as phenols and phenol sulfides, may also be present.

The lubricating oil base stocks used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from paraflinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. Hydrogenated oils or white oils may be employed. Synthetic oils such as the polyether and polyester types or those prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products may be used as such or in combination with each other and/ or with mineral base lubricants. In certain instances cracking coil tar fractions and coal tar or shale oil distillates may also be used.

The additives are normally sufficiently soluble in the lubricant base stock, but in some cases auxiliary solvent agents may be used. The lubricating oils will usually range from about 40 to 150 seconds (Saybolt) viscosity at 210 F. The viscosity index may range from to 100 or even higher.

Other agents than those which have been mentioned may be present in the oil composition, such as dyes, pour point depressants, heat thickened fatty oils, sulfurized fatty oils, sludge dispersers, anti-oxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, and the like.

In addition to being employed in lubricants, the additives of the present invention may also be employed in other mineral oil compositions and hydrocarbon products. These include motor fuels, mineral oil base hydraulic fluids, torque converter fluids, cutting oils, flushing oils, turbine oils, transformer oils, industrial oils, process oils, gear lubricans, greases, etc.

Below are given detailed descriptions of preparations of several examples of mineral oil additives of the type described above as well as various laboratory tests which were applied to determine their effectiveness when employed in lubricating oil compositions. It is to be understood that these examples are given to illustrate the present invention and are not to be construed as limiting the scope thereof in any way.

EXAMPLE I.PREPARATION OF PRODUCTS Product A.Ester 0f 1-hydraxy-n-butylph0sphonic acid and tertiary octylphenol sulfide A 3-way flask equipped with a stirrer and a return condenser attached through a water trap, was charged with 88.4 gms. (0.2 mol) of crystalline tertiary-octylphenol and 30.6 gms. (0.2 mol) of hydroXy-n-butyl phosphonic acid. To this was then added 200 ml. of xylene and one ml. of concentrated sulfuric acid. Then, while the mixture was refluxed, water of formation was removed by means of the water trap. The heating was continued until 6 ml. of water were caught in the water trap.

The mixture was then cooled, poured into water, and extracted with ether. The extract was washed several times with water and finally dried over sodium sulfate. On removal of the solvent, 107 gms. of viscous red oil were obtained as a residue which may be designated as Product A.

Product B.-Calcium salt of Product A A portion of Product A was dissolved in ether and added slowly with rapid stirring to a suspension of calcium hydroxide in 200 cc. of ice and water. The mixture was then extracted with ether and dried over Drierite. On removal of the solvent at 100 C. under reduced pressure, 69 gms. of light colored, readily pulven'zable salt was obtained, designated as Product B. The latter was readily soluble in mineral oil.

Product C.-Calcium salt of l-hydroxy-n-butyl octadecenylphosphonate A 3-way flask equipped with 'a stirrer and a return condenser attached through a water trap, was charged with 46.2 gms. (0.3 mol) of n-butyl-hydroxyphosphonic acid, 80.4 gms. (0.3 mol) of oleyl alcohol, and about 50 cc. of xylene. Then, while the mixture was refluxed with rapid stirring, the water of formation was removed by means of the water trap. By the time that 5 ml. of water were collected, all the phosphonic acid had dissolved. A total of 6 ml. of water were obtained.

The mixture was then cooled and diluted with ether. The ether solution was then added with rapid stirring to a suspension of 11.1 gms. of calcium hydroxide in 200 ml. of water. The ether layer was then separated from the water layer and was dried over calcium sulfate. On removal of the ether, 104 gms. of viscous red oil were obtained. The product contained 3.85% calcium and 7.68% of phosphorus.

Product D.-Calcium salt of the ester of l-hydroxy-nbutylphosphonic acid and sulfurized oleyl alcohol A 3-way flask equipped with a stirrer and a return condenser attached through a water trap, was charged with 53.6 gms. sulfurized oleyl alcohol, 24.6 gms. of l-hydroxy-n-butylphosphonic acid, and 20 ml. xylene.

The mixture was then refluxed with rapid stirring. The water formed was collected in the water trap. The acid gradually dissolved as the reaction proceeded. When no more water was given 013?, the solvent was removed at C. under 3 mm. pressure. The residue was dissolved in ether, and added slowly with stirring to asnspension of a slight excess of calcium hydroxide in water. The ether extract was dried over calcium chloride. On removal of the ether, the residue was dissolved in naphtha and filtered to remove a small amount of insoluble material. On removal of the solvent, 55 gms. of light brown solid was obtained. The latter was found to contain 3.28% calcium, 6.32% phosphorus, and 7.27% sulfur. The product was readily soluble in naphthenic mineral oils and somewhat less soluble in parafiinic mineral oils.

Product E.Calcium salt of the condensate of 1 -hya'r0xyn-buzyl-octadecenyl phosphonate and phosphorus pentasulfide 1-hydroxy-n-butyl-octadecenyl n-butylphosphonate was prepared as described in the case of Product C. This was then condensed with phosphorus pentasulfide as follows.

A 3-way flask equipped with a stirrer and return condenser was charged with 200 ml. dioxane, 16.65 grns. (0.075 mol) phosphorus pentasulfide and 125 gms. (0.42 mol) of the octadecenyl phosphonate. The mixture was then refluxed until no more hydrogen sulfide was given ofi. The product was then filtered off from a small amount of undissolved material and evaporated to dryness under reduced pressure. The residue consisted of gms. of viscous light brown oil.

The above described oil was suspended in water and neutralized with sodium hydroxide using phenolphthalein as an indicator. To this was then added 50 gms. of calcium chloride dissolved in water. The soap, which separated as a water insoluble oil, was extracted with ether and dried over calcium chloride. On removal of the solvent at 100 C. under 3 mm. pressure, the residue was obtained as a light-colored viscous oil which proved to be readily soluble in mineral oils. It contained 4.88% calcium and 5.13% phosphorus.

EXAMPLE II.--CARBON BLACK DISPERSION TEST was agitated with 6% by weight of carbon black and a1 7 a lowed to settle for 24 hours at a temperature of 200 F. For comparison, a similar amount of the base oil was treated in the same manner. The results are shown in Table I below:

It is seen that the various metal salts of the present invention gave perfect dispersion of carbon black in oil.

EXAMPLE III.-BEARING CORROSION TEST Blends were prepared containing 1% of the various products in a lubricating oil base consisting of a well refined, solvent extracted paraflinic mineral lubricating oil of S. A. E. 20 viscosity grade. These blends and a sample of the unblended base oil were submitted to a corrosion test designed to test the effectiveness of the additive in inhibiting corrosion of a typical copper-lead bearmg.

In this test 500 cc. of the oil were placed in a glass oxidation tube (13 inches long and 2% inches in diameter) fitted at the bottom with a /1 inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. Two quarter sections of automotive bearings of copperlead alloy of known weight havinga total area of 25 square centimeters were attached to opposite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. M., thus providing sufiicient.

agitation of the sample during the test. Air was then blown through the oil at a rate of 2 cubic feet per hour. At the end of each 4-hour period the bearings were re moved, washed with naphtha, and weighed to determine the amount of loss by corrosion. The bearings were then repolished (to increase the severity of the test), reweighed, and then subjected to the test for additional 4-hour periods in like manner. The results are given in Table H, below, as corrosion life, which indicates the'number of hours required for the bearings to lose 100 mg. in weight,

. 8v determined by interpolation of the data obtained in the various periods.

TABLE II Additive tested: Bearing corrosion life, hours Base nil 6 0.5% Product A 9 0.5% Product R 18 0.5% Product C 14 What is claimed is:

1. A lubricating oil composition containing dissolved therein in a range of about 0.01 to 15% by weight of the calcium salt of the partial ester of l-hydroxy-phosphonic acid having the formula:

wherein R1 is selected from the group consisting of hydrogen and hydrocarbon radicals having in the range of 1 to 12 carbon atoms, and R2 is a radical of tertiary octylphenol sulfide.

2. A mineral lubricating oil containing dissolved therein in the range of about 20 to by weight of the calcium salt of the partial ester of l-hydroxy-n-butylphosphonic acid and tertiary octylphenol sulfide.

3. A lubricating oil composition containing dissolved therein in a range of about 0.01 to 15% by weight of the calcium salt of the partial ester of l-hydroxy-n-butylphosphonic acid and tertiary octylphenol sulfide.

4. A mineral lubricating oil containing dissolved therein in the range of about 0.01 to 15 by weight of the calcium salt of the partial ester of 1-hydroxy-n-butylphosphonic acid and tert.-octylphenol sulfide.

References Cited in the file of this patent UNITED STATES PATENTS 2,228,671 Neely Ian. 14, 1941 2,279,502 Dickey et a1. Apr. 14, 1942 2,311,305 Ritchey Feb. 16, 1943 2,420,893 McNab May 20, 1947 2,476,813 Buckmann July 19, 1949 2,506,310 Mikeska May 2, 1950 2,579,810 Fields Dec. 25, 1951 FOREIGN PATENTS 549,296 Great Britain Nov. 16, 1942 552,061 Great Britain Mar. 22, 1943 

1. A LUBRICATING OIL COMPOSITION CONTAINING DISSOLVED THEREIN IN A RANGE OF ABOUT 0.01 TO 15% BY WEIGHT OF THE CALCIUM SALT OF THE PARTIAL ESTER OF 1-HYDROXY-PHOSPHONIC ACID HAVING THE FORMULA 